1. Technical Field
The present invention relates to a microlens used for an electro-optical device such as a liquid crystal device, to a microlens array, to a method of manufacturing the same, and to an electro-optical device, and to an electronic apparatus having microlenses.
2. Related Art
In an electro-optical device such as a liquid crystal device, for example, a microlens corresponding to each pixel is formed on a counter substrate or a microlens array plate including a plurality of microlenses is bonded to the counter substrate. By using such a microlens array, a bright display can be realized in an electro-optical device. That is, the microlenses increase the usage efficiency of light emitted from a light source by causing the light emitted from the light source, such as a backlight, to be focused on an opening region of each pixel without wasting any light. For example, a liquid crystal device including such microlenses is manufactured as follows. A counter substrate having a built-in microlens array, and an element substrate where pixel electrodes or switching elements, such as thin film transistors and so forth, are formed at respective pixels are sealed by a bonding resin in a portion excluding the image display region while adjusting a gap therebetween, and liquid crystal is interposed therebetween and then encapsulated.
In the above-described liquid crystal device, it is essential to make the thickness of the liquid crystal layer uniform over the entire liquid crystal panel in order to reduce non-uniform luminance and color shading. Japanese Unexamined Patent Application Publication No. 2000-193928 discloses a technique in which a circumferential part of each microlens is curved while a central part of the microlens is flat. By doing this, the thickness of the resin layer formed on the microlens becomes thin due to the reduced thickness of the microlens, and as a result, thickness variation of the liquid crystal layer is reduced.
In such electro-optical devices, there is a general request for devices with a long lifetime.
However, when a microlens is employed, typically, light emitted from the light source is locally focused via the microlens on a portion positioned at the center of an opening region of each pixel, for example, of a liquid crystal or an orientation layer: the inventors have found that deterioration was significant in this portion.
Further, the related art disclosed in Japanese Unexamined Patent Application Publication No. 2000-193928 is directed to a technique for reducing a thickness variation of the liquid crystal layer: this technique is not regarded as a technique of recognizing deterioration within the pixel region due to focusing, which has been found by the inventors. Furthermore, the inventors expect that the lens characteristics of the microlens are not good because the central portion of the microlens is flat. That is, the microlens disclosed in Japanese Unexamined Patent Application Publication No. 2000-193928 does not focus light incident on the central portion, which is a flat surface, but instead allows the light to be transmitted straight through, so that the central portion does not function as a lens. Accordingly, it is difficult to enhance the light usage efficiency by effectively focusing light within the opening region, so that it is difficult to enhance the display luminance and contrast.